EpocCam HD App

I'm using Kinoni EpocCam app the pro version that cost 5.99 and the reason I bout it , is because the HD version had microphone privileges but when I the HE version of the app I couldn't figure out how to use the microphone on the app and it asked for microphone privileges after I launched it when it finished downloading. Pls, help me figure out how to use my microphone on my iPhone to be able to hear myself when I use the app to mirror on my desktop